An edimmu is a Slayer monster in Daemonheim that can be killed with level 90 Slayer. It attacks players with a fairly accurate red orb magic attack and uses melee when its target is adjacent to it. Additionally, this red orb heals the Edimmu for the damage in which it hits. It is weak against slashing weapons, so those with longswords, battleaxes, and two-handed swords will be able to dispatch it without too much trouble.

Edimmu are much sought after for their Blood necklace drops. However, it is rare to see an Edimmu; there have been sightings on furnished floors and they appear very rarely on abandoned floors, but the likelihood of encountering one becomes greater on the Occult floors and even better on Warped floors. Having more high level slayers in your team helps, but does not guarantee an encounter.

The Blood Necklace used to have a 30 second limit before it could be picked up. Only the one who dealt the most damage was able to pick it up instantly. However, this was removed in the Evolution of Combat update, currently whoever hits the monster first will receive the drop, as if they did the most damage.

As of 19 April 2012, Slayer monster frequency in Dungeons has been increased by nearly double, making encountering an Edimmu a far more common occurrence on attempted floors than they previously were.

On 10 September 2013 Dungeoneering Hard Mode was released along with the Daemonheim task set. On Hard Mode floors, slayer monsters, such as the Edimmu, are significantly more common encounters.

In Sumerian mythology, Edimmu were the ghosts of people who were not buried properly, they were classified as a type of Utukku; A good or bad spirit. Edimmu were a type of evil being, or Asakku.

It is believed in some circles that Edimmu were a form of psychic vampire. They were referred to as "evil wind gusts; 'wind' could have been used to mean 'breath', and some Occult studies posit that breath is directly related to the transfer of psychic energy.

The edimmu's appearance looks like a ghost emitting from a corpse, presumably rotted and decapitated. This fits their background, with the ghost not being able to detach from the corpse, due to not being buried properly.

Prior to the update of 10 November 2014, Edimmus were only found while Dungeoneering.